Technical Abstract:
This study reports the production and characterization of a novel antibacterial polypeptide, designated as laparaxin, which is secreted by Lactobacillus paracasei NRRL B-50314. The crude laparaxin has antibacterial activity against a range of Gram-positive bacteria including the following: lactic acid bacteria strains Lactococcus lactis LM 0230 and Lactobacillus buchneri NRRL B-30929 (isolated from a bio-ethanol production facility); the food-borne pathogen Listeria monocytogenes; the gastrointestinal pathogen Enterococcus faecalis; strains of the opportunistic pathogen Staphylococcus aureus including methicillin-resistant S. aureus (MRSA) 592S, 209P, 1316V5, 1316V20, DU496S, and a hetero-vancomycin-intermediate methicillin resistant strain (HVI-MRSA) MM66. Using L. lactis as an indicator strain, the inhibitory activity of crude laparaxin was detected initially in early log phase, and the activity maximizes at the early stationary phase and remains stable after prolonged incubation. Laparaxin activity is stable when incubated at 94**oC for 30 min. Higher concentrations of inhibitory activity are produced when glucose, fructose, and sucrose were used as carbon-sources in growth media. The crude laparaxin has potential applications in food and feed industry as well as in clinical and veterinary medicine.